SGA technology may be desirable for panel level processing because an SGA configuration may typically only involve printing solder paste on a strip or panel, and then performing a reflow process resulting in formation of bumps. The SGA solder paste may include a powder mixed with a flux. However, typically the incoming strips/panels may be warped at room temperature, and hence in order for the SGA bumps to be coplanar post reflow, the strips/panels may have to be flattened so that the SGA bumps are uniformly deposited across the strip/panel. One technique for doing so may include heating the strips/panels to a temperature as high as 80 degree Celsius (° C.) prior to printing the SGA bumps. This heating step may cause the strips/panels to flatten significantly such that the SGA bumps may be more uniformly deposited.
However, a consequence of pre-heating the strips/panels may be that the strips/panels are still heated when the SGA bumps are deposited, resulting in the SGA paste being exposed to significant amounts of heat prior to reflow. However, some legacy solder pastes may not be able to withstand the heating and may significantly deteriorate, which may lead to cracking or flux/powder separation of resultant post-reflow solder joints. This deterioration may increase with increasing fineness of the powder used in the solder paste to make SGA bumps with a pitch of less than 0.3 millimeters (mm).
Some legacy techniques that have been tried to address the above-described drawbacks of pre-heated SGA bumps have included a flux+microball technology. However, flux+microball may be more costly compared to SGA. Additionally, the flux used in flux+microball techniques may still need to be printed at a higher temperature, and therefore some legacy fluxes may still suffer from deterioration.